Deuteronomy 20:15

Overview - Deuteronomy 20
1	The priest's exhortation to encourage the people to battle.
5	The officers' proclamation of who are to be dismissed from the war.
10	How to use the cities that accept or refuse the proclamation of peace.
16	What cities must be devoted.
19	Trees of man's meat must not be destroyed in the siege.

Deuteronomy 20:15  (King James Version)
Thus shalt thou do unto all the cities which are very far off from thee, which are not of the cities of these nations.